Children with Asthma at Higher Risk for Hospitalization on Warm Smoggy Days

8:44 February 8, 2010

The new study, published in the Journal of Allergy and Clinical Immunology, was based on data collected from 74 hospitals in all five New York City boroughs, involving more than 75,000 asthma-related hospitalizations from 1999 to 2006. The study provides substantial evidence that the pollution that settles into the air in warmer seasons increases the risk that a child with asthma will have an episode severe enough to require hospitalization.

“This is a major problem,” said Robert A. Silverman, MD, research director for the LIJ Medical Center Emergency Department, associate professor of emergency medicine at the Albert Einstein College of Medicine in the Bronx and an associate investigator at The Feinstein Institute for Medical Research in Manhasset, NY.

Dr. Silverman, Kazuhiko Ito, PhD, an environmental scientist at the NYU Nelson School of Environmental Medicine and other researchers utilized air pollution data from 37 federally-placed monitors situated throughout the New York City metro area that are used by the US Environmental Protection Agency (EPA) to measure air pollutants. Twenty-four of the sites measure small particle emissions and 13 monitor the ambient air for ozone. Investigators focused on the warm weather months because ozone levels are at their highest and small-particle pollution is also high. Ozone levels are generally higher in the warmer months because heat and sunlight enhance the production of ozone – a chemical component of the smog formed by a reaction of pollutants from cars, factories and gas vapors. The main sources of small particle air pollution in the eastern United States during the summer, also known as PM 2.5, are coal-burning power plants in the Ohio Valley region and local traffic.

Dr. Ito compared the asthma-related hospital admissions to the varying levels of air pollutants between April and August. They found substantial increases in the number of hospital admissions in children on days when small particles and ozone were elevated, and that the prevalence of asthma hospitalizations was more common among children than adults. In fact, in children between the ages of 6 and 18, there was an approximately 20 percent increase in asthma hospitalizations on higher small particle days and a 26 percent increase in admissions to the intensive care unit (ICU). For ozone, it was a 19 percent increase in ICU admissions and higher ozone days.

“Children were far more vulnerable,” wrote Drs. Silverman and Ito. By comparison, adults over age 50 had a three percent increased risk of hospital admission on high small particle days and a six percent increase on high ozone days. In 19-to-49 year olds, there was an eight percent increased risk for hospitalization on high-pollution days.

Importantly, increases in air pollution were also associated with life- threatening asthma that required an admission to an ICU. This association was seen primarily in school-aged children. In the study, about one out of 10 children between the ages of 6 and 18 hospitalized for asthma was admitted to the ICU. There did not seem to be an increased risk for older adult asthma sufferers to land in the ICU.

Dr. Silverman said that there was a direct correlation between age and the risk for asthma-related hospitalizations. Children under age six did not have the same high risk as school-aged children having the highest risks. The older people get, the lower the risk. Dr. Silverman said he thinks that this may be because school-aged children are more likely to play outdoors and take in more air pollution, which is a trigger for asthma. “Children also normally have faster breathing than adults, and their lungs and immune systems are still developing. They are more sensitive to the harmful effects of air pollution,” he said.

They also looked at the measures of air pollution and found that there was no threshold of pollution that was safe.” The higher the air pollution concentrations, the scientists said, the greater the risk for a severe asthma attack.

The EPA is now holding hearings on whether to reduce the acceptable safety threshold for air pollutants. “EPA scientists need to revise what safe levels are,” Drs. Silverman and Ito wrote. “These levels should take into account the fact that children are more sensitive to air pollution.”

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